This invention generally relates to fluid transfer mechanisms for aspirating, transferring, and dispensing fluids, and more particularly to such mechanisms employed in high speed, laboratory analysis instruments.
In modern laboratory analysis, for example analysis of blood serums, large numbers of serum samples, control samples, and reagents must be processed in high speed, automatic equipment. In such equipment, a typical arm mechanism carries a probe for sequentially aspirating multiple fluid aliquots which are then transferred and dispensed into analysis vessels positioned remotely from the aspiration.
In copending United States Patent Application Ser. No. 115,691, filed Jan. 28, 1980, entitled Fluid Transfer Mechanism, now U.S. Pat. No. 4,276,260 which is incorporated herein by reference, DRBAL et al describe a fluid probe carried on an arm mechanism which can be vertically translated at high speed on a high helix shaft and rotated around the shaft by an additional drive. The described probe mechanism further includes a slide structure for stirring fluids by linear oscillation of the probe which also carries connections to a liquid, level-sensing circuit; the arm further includes a light switch which can signal when the light path is interrupted by separately mounted tabs which indicate vertical positions of the arm for monitor and control. Such instruments provide very precise vertical and horizontal positioning of the fluid probe for aspirating and dispensing operations; however, a recurring problem arises in automatic equipment of this type when lead wires of the electrical components are carried on the moving arm, and the motion of the arm or its components causes winding or kinking in lengths of the leads. In extreme situations the motion of the leads can produce resistance or interference with the required motion of the arm.